Folded optical system for radiation detection device

Abstract

A folded modular optical system adapted for use, for example, in a passive infrared intruder detection device for directing radiation from a plurality of discrete fields of view onto a radiation-sensitive detector comprises an elongated rectangularly-shaped spherical reflector and a multifaceted reflective element. The latter comprises a plurality of elongated, generally parallel, planar reflectors which serve to direct radiation onto different portions of the spherical reflector. To minimize the effects of spherical aberration, the planar reflectors are arranged so that the portions of the spherical reflector which they irradiate are substantially perpendicular to the longer dimension of the rectangularly-shaped spherical reflector. Preferably, each of the planar reflectors is canted relative to the others so that its field of view is substantially co-planar with those of the other planar reflectors. It is also preferred that the planar reflectors vary in size and, hence, light-gathering power as a function of the intended range of protection they provide.

I claim: 
     
       1. A folded modular optical system for use in radiation detection devices for directing radiation from a plurality of fields of view onto a radiation-sensitive detector, said system comprising an elongated rectangularly-shaped spherical reflector, and a multifaceted reflective element having a plurality of planar reflectors, each of said planar reflectors being arranged to reflect radiation from a discretely different field of view onto a different portion of said spherical reflector, each of said portions having a dimension measured in a direction parallel to the longer dimension of said spherical reflector, which is only a fraction of said longer dimension. 
     
     
       2. The invention as defined in claim 1 wherein said spherical reflector is arranged with its optical axis in a vertical plane, wherein each planar reflector is arranged at a different tilt angle relative to the horizontal plane, such that the field of view of each planar reflector is directed below the horizontal at a different angle, and wherein the area of at least some of the planar reflectors is proportional to its tilt angle. 
     
     
       3. The invention as defined in claim 1 wherein said planar mirrors are canted relative to each other so that their respective fields of view are substantially co-planar. 
     
     
       4. A folded modular optical system comprising an elongated spherical reflector and a plurality of planar reflectors, each of said planar reflectors cooperating with a different portion of the spherical reflector to focus radiation emanating from a plurality of different fields of view, said portions having a dimension, measured in a direction parallel to the length of the spherical reflector, which is less than one-half said length. 
     
     
       5. The invention as defined in claim 4 wherein (a) said spherical reflector is arranged with its optical axis extending upwardly, (b) each planar reflector is arranged at a different tilt angle relative to the horizontal plane such that the field of view of each planar reflector is directed below the horizontal at a different angle, and (c) the area of at least some the planar reflectors is proportional to their respective tilt angle. 
     
     
       6. The invention as defined in claim 4 wherein said planar reflectors are canted relative to each other so that their respective fields of view are substantially co-planar.